A proponent of the leftist politics that preceded World War II, Kruczkowski published his first novel, Kordian i cham (“Kordian and the Boor”), in 1932. It was—as the author himself put it—“an attempt to show the peasant question in Poland from the broad perspectives of historical development.” Using the Marxist view of the historical process, Kruczkowski saw the causes of the November 1830 Polish insurrection against Russian rule in the light of class struggle. He continued his social and historical analysis in the novels Pawie pióra (1935; “Peacock’s Feathers”) and Sidła (1937; “The Trap”).

Captured as a soldier in 1939, Kruczkowski spent World War II in a prison camp. After the war he joined the Polish Communist Party and was a prominent activist in state and party affairs. His finest play, Niemcy (1949; “The Germans”), analyzed the rapid spread of Nazi ideology among the German people. His drama Juliusz i Ethel (1954; “Julius and Ethel”) presented the case of Julius and Ethel Rosenberg, whom the U.S. government had sentenced as Soviet spies and executed. Kruczkowski depicted them as innocent victims of a political plot. In Pierwszy dzień wolności (1960; “The First Day of Freedom”; filmed 1965), he reflected on the conflict between human freedom and historical necessity. His last play, Śmierć gubernatora (1961; “Death of a Governor”), examined the ethics of the capitalist world, to which Kruczkowski compared the humanitarian principles of the socialist camp.